Cotton fabrics are often treated with crosslinking resins (also referred to as “reactants”) to impart wrinkle resistance during wear and after multiple launderings. The crosslinking not only imparts durable smoothness and shape retention to the fabrics, but also improves shrinkage control and inhibits pilling and fuzzing of the fabric surface. Other benefits of crosslinking include, but are not limited to, quicker drying and easier pressing, where that may be necessary.
The crosslinking process, however, also has some disadvantages. There is a loss of abrasion resistance and strength, which results in a decreased wear life. A number of methods have been developed over the years to lessen the impact of these deteriorating effects. Some of these technologies have been adopted while other proposed methods have been too expensive.
Many of the commercial reactants that are used to impart wrinkle resistance also have the disadvantage of releasing formaldehyde, either during the mixing and application of such reactants in the textile mill, or after they have been applied to fabric. In recent years, the World Health Organization (WHO) has classified formaldehyde as carcinogen (International Agency for Research on Cancer (IRAC), Press Release No. 153, Jun. 15, 2004). Recently, the European Chemicals Agency (ECHA) released the following statement, “Formaldehyde is classified as category 1B carcinogen with a CLP concentration limit of ≥0.1%1. The Commission has proposed to include formaldehyde and some formaldehyde releasers in the next amendment to Annex XVII to include CMR substances 1A and 1B in the Appendixes to restriction entries 28-30 to Annex XVII. This will restrict the placing on the market for supply to the general public of formaldehyde and included formaldehyde releasers in mixtures with the respective concentration limits set by the CLP regulation will be included.” Available at: www.echa.europa.eu/documents/10162/13641/formaldehyde_review_report_en.pdf/5 51df4a2-28c4-2fa9-98ec-c8d53e2bf0fc.
Over the years, reactants, such as dimethyloldihydroxyethyleneurea (DMDHEU), have been modified to lessen the release of formaldehyde, but these products are not completely free of formaldehyde. See, e.g., B. Li, Y. Dong, P. Wang, and G. Cui, Release behavior and kinetic evaluation of formaldehyde from cotton clothing fabrics finished with DMDHEU-based durable press agents in water and synthetic sweat solution, Textile Research Journal, Vol 86 (16), 1738-1749 (2016).
Several non-formaldehyde reactants have been developed and tested over time, but many have drawbacks in terms of yellowing, latent odor development on fabric, cost, or poor performance. Recently, reactants that are based on modified dimethylurea/glyoxal (DMUG) chemistry have been developed and applied in a fashion to achieve wrinkle resistance comparable to DMDHEU without formaldehyde release or the aforementioned drawbacks of yellowing and latent odor. The use of modified DMUG chemistry alone, however, does not solve the problem of loss of abrasion resistance and strength associated with non-formaldehyde reactants.